It is now very popular to distribute various kinds of software data, for example, audio data such music data, image data such as movie data, game programs, and application programs, via a network such as the Internet or via an information storage medium such as a CD (Compact Disc) or a DVD (Digital Versatile Disk). These distributed contents are played back and used on a PC (Personal Computer) of a user, a playback apparatus such as a CD player, a DVD player, or an MD player, or a game machine.
In general, the right of distribution of software contents such as music data or image data is held by producers or sellers of the software contents. Software contents are generally distributed under specific usage limitation to secure that only authorized users can use software contents and that unauthorized copies thereof cannot be made.
In recent years, it has become popular to digitally store information on a storage medium using a recording apparatus. Digital storage on a storage medium using a digital recording apparatus allows it to repeatedly store and play back image data or audio data without causing degradation. That is, it is possible to make copies of digital data many times without causing degradation in image quality or sound quality. However, this has brought about a problem that a large number of unauthorized disks, such as CD-R on which unauthorized copies of contents are stored, are illegally distributed.
Such illegal distributions of unauthorized storage media in markets cause losses of profits of owners of copyrights or distribution rights of contents such as music or movie contents.